Subscriber receiver enunciator



Patented Dec. 29, 1953 John R. Rowland, Lake Fbrest; 111;. assignorntt', Zenith Radio Corporation; a cbrp'oration of Illinois Applic tion Mar :10, 1950, Seria1Nm .61.08 3 Claims; (01. 178-521) This invention relates to su'oscriptionsignalling systems in which a coded signal is transmitted over one channel and a key signal for decoding the coded signal is transmitted to subscriber receivers over a second channel, preferably a line circuit. More specifically, this invention relates to a signalling device or enunciator which is adapted to be connected into a subscriber receiver for indicating under certain conditions the receipt for the key signal over the line circuit.

Subscription signalling systems of the type under consideration are disclosed in Patent 2,510,046, filed in the name of Ellett et al., and issued May 30, 1950, entitled Radio-Wire Signalling System" and Patent 2,547,598, filed in the name of Roschke and issued on Aprile, 1951-, entitled Image Transmission System, both of which are'assigned to the present assignee. The

receiver arrangements of these systems are con-" structed to utilize standard uncoded television signals as well as coded subscription television signals. It is contemplated that a subscriber wishing to view a program transmitted by a'coded subscription signal will call a central ofiice'and' request that the appropriate key signal for decoding the subscription signal be disseminated to his receiver over the telephone circuit at the proper time. The subscriber may order the key signal some time during the day of the subscription broadcast well in advance of the time at which reception of the key signal is desired and. of course, it-is possible-that the subscriber may forget the program and may even forget that heflhas ordered thekey signal required for enjoying the program. In fact, he-may beutiliaiug his television receiver for the receipt of a stand ard uncoded television broadcast during the time of the subscription program for which he has ordered the key or decoding signal. Should this occur, the key signal is nevertheless supplied to the subscriber and he is charged therefor; even though he is deriving no benefit from' the key signal.

The purpose of the presentinvention'i's topic-- vide an enunciator which indicates the receipt of the key signal under such circumstances, preferably. by an audible signal. This signal. commences the moment that the key signal. is supceiver toindicate the receipt of a key signal during operating intervals in which the receiver is not conditioned to use thekey signal for decoding a subscription broadcast.

The features of this invention which are believed to be neware" set forth with particularity in the appended claims. The invention itself, however, together with further objects and advantages thereof ma'y'b'est be understood by referenceto the following description when taken in conjunction with the accompanying drawing in which the single figure shows a preferred embodiment of' the invention incorporated into a subscription type television receiver.

The subscription receiver illustrated is disclosed'and described in detail in Patent 2,547,593 referred to above. However, it will be understood that the present invention may be inc0rporated into any type of subscription receiver which utilizes a separately received'key signal to decode the coded subscription signal. Moreover, the various components of'the subscription receiver are shown in block form since these components are either well'known to the art or described in great detail in the Roschke patent and of themselves form no part of the present invention;

The receiver includes a radio-frequency amplifier f0 of one or more stages, this amplifier being-connected to a first detector H. The output terminals of detector H are connected to an intermediate-frequency amplifier i2 of any desired number of stages, and this'amplifier is connected-tea seconddetector l3. The second detector I3 is connected to a video amplifier" H3 of any suitable number of stages; and the output terminals of amplifier I are connected to the plied to the subscriber if his receiver is not-tuned to the subscription broadcast, and continues until the receiver is tuned to recei'vethe subscription pr gram which thekey signal is inten;dedto code.

It is, accordingly, an object ofthe present invention to provide a device for a subscriber reinput electrodes of an image-reproducing device 1 5 to control the intensity of the cathode ray therein-in accordance with the video intelligence of a received television signal. The input terminals of radic frequency amplifier" in maybe connected: to any suitable"antehnalcircuit' IE5, H.

The video amplifier 14 may be connected to a .is ynchronizing. signalsep'arator l8, and the separator connected to ,a field-sweep generator 19 and-through a decoding circuit 20 to a line-sweep generatorzl. Theoutput terminals of generators I9 and .z'l'areconnec'ted respectively to the fieldiandlline-deflcction.elements 22 and 23 of reproducing tube .15. The second detector l3 is connected re the sound hannel or the receiver which inclu a limiter-discriminator sta e 24,

an audio amjPlmer' -25 and a sauna-reproducin device ,2'6.= I

The receiver is connected to a" subscription transmitter or to any other source supplying the necessary decoding or key signal by means of a line circuit 21 which may conveniently be a telephone network. The line circuit 21 is connected to an amplifier 28, and the output terminals of this amplifier are connected to a control circuit 29 through a switching device 30. The control circuit 29 is also connected to field-sweep generator I9 to derive field-blanking pulses therefrom.

As fully described in the Roschke patent, the

for example, to have the amplitude-time characteristic of the key signal very precisely in accordance with the coding schedule of th transmitter.

The coded television signal may be intercepted by the antenna circuit I6, I! and amplifiedi in radio-frequency amplifier I0. Thence, it is heterodyned to the selected intermediate frequency of the receiver in first detector H" and the resulting intermediate-frequency signal is amplified in amplifier l2 and detected in second detector i3. The composite video signal derived from the second detector is amplified in video amplifier I4 and applied to the input electrodes of tube Hi to modulate the cathode-ray beam thereqi in well-known fashion.

The synchronizing components of the received television signal are separated from the video information in the synchronizing-signal separator and applied to field-sweep generator l9. This generator is synchronized by the field-synchronizing components of the received signal and controls the field scansion of tube I5. The synchronizing components are further applied to line-sweep generator 2| through decoding circuit to control the line scansion of tube l5. As previously stated, during spaced intervals the timing of the video components of the received signal is varied relative to the line-synchronizing components by a preselected amount. The decoding circuit 2!] is constructed to impart a time delay to the line-synchronizing component as applied to line-sweep generator 2| corresponding to this preselected amount. This decoding is under the control of unit 29 which, in turn, acts in response to field-blanking pulses derived from generator |9 and the key signal derived from am- Since the key signal represents the coding schedule of the subscription transmitter, the decoding circuit is actuated during the appropriate spaced intervals to compensate for the variations in timing of the components of the received subscription signal. In this manner, the timing of the line scansion of reproducingtube I5 is altered by the correct amount and in the appropriate sense so that tube l5 may reproduce the intelligence contained inthe received television signal. The receiver thus far described is completely disclosed in the above-identified Roschke patent, and since it forms no part of the present invention, a more detailed description thereof is deemed to be unnecessary.

In accordance with th principles of inter-carrier sound, now well known to the art, an interpacitor 31.

carrier signal frequency modulated with the sound components of the received television signal may be derived from second detector 3 I. This inter-carrier signal is applied to limiter discriminator 24 wherein the audio intelligence is recovered. This audio intelligence is amplified in audio amplifier 25 and reproduced in sound- :reproducing device 26.

In order that the subscriber may be informed of the receipt of the key signal on line circuit 21, when his receiver is not conditioned to accept and use that signal, an enunciator circuit comprising an electron-discharge device 3| is included in the receiver. A control electrode 32 of device 3| is coupled to one of the output teriminals of amplifier 28 through a capacitor 33, and is connected to ground through a grid-leak resistor 34, the other output terminal of amplifier 28 being also connected to ground. The cath- +ode 35 of device 3| is connected to ground through a cathode resistor 36 shunted by a by-passsca- The anode 38 of device 3| is connected to the positive terminal B+ of a source of unidirectional potential through a load resistor 39, and cathode 35 is also connected to this terminal through a resistor m series-connected with a switching device 4 l. The switching device 4| is mechanically coupled to the previously mentioned switching device3il as shown. The anode 38 is connected to the sound-reproducing device 26 through a normally closed switch element 42.

The switch 30 is provided to disconnect the receiver from line circuit 2'! during the reception of standard uncoded television signals. Obviously, while this switch is open the circuit from the line amplifier 28 to the control unit 29 is interrupted and the receiver cannot properly respond to a subscription broadcast. Should that condition exist during a particular subscription broadcast to which the receiving station has subscribed, a key signal is received over line circuit 21 and after amplification in amplifier 28 is translated by device 3| and delivered to sound-reproducing device 26. The key signal may be of an audible frequency so that an audible tone is developed indicating the receipt of the key signal to the subscriber. Upon this indication, the subscriber tunes the receiver to the subscription channel and closes switch 30 so that the key signal is delivered to control circuit 29 and the receiver is conditioned to decode the received subscription signal. Closure of switch 30 completes the circuit of the potentiometer arrangement of resistors 36 and 40 through switch element 4| and causes device 3| to be biased to a non-conductive state so that the key signal is no longer tran lated thereby and the corresponding tone in reproducing device 26 is discontinued.

Should a subscriber retain switch 3%] in' a closed position while utilizing his receiver for the reception of uncoded television signals, device 3| is biased to cut-off and no key-signal tone occurs in reproducing device 26 upon the reception of the key signal. However, under this condition there is no need for such indication because the key signal'actuates decoding device 20 and causes distortion in the reproduction of the uncoded television signals. Conseouently the subscriber is immediately aware of the fact that the key signal is being received and tunes his receiver to the subscription channel.

The situation may arise wherein the subscriber desires to tune his receiver to. a standard uncoded television signal and yet does not wish to discontinue the key signal by a call to the central office. In order that the received key signal will have no efiect 0n the uncoded signal, the operator must open switch 30. This, however, causes switch 4| to open and gives rise to a tone in reproducing device 26. ,To discontinue this tone, switch element 42 may be opened. It is desirable that switch 42 be mechanically coupled to a contact 43 which completes the circuit between a potential source 44 and an indicating lamp 45 whenever the switch 42 is open.

It is pointed out, that although the sound-reproducing device 26 may conveniently be used to produce an audible tone signal upon the receipt of the key signal, separate buzzers or other indicating means responsive to the key signal may be used when so desired.

This invention provides, therefore, a signalling device or enunciator for use in a subscription receiver of the type which utilizes a key received over one channel to decode a coded subscription signal received over a second channel. The enunciator of the present invention acts to inform a subscriber of the receipt of the key signal, and continues to operate until the receiver is tuned to the appropriate subscription signal at which time the enunciator circuit is disabled.

While a particular embodiment of the invention has been shown and described, modifications may be made and it is intended in the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

I claim:

1. In a receiver for utilizing a television signal coded in accordance with a prescribed coding schedule, an image-reproducing device, apparatus for receiving said television signal and for supplying said signal to said reproducing device, a decoding mechanism coupled to said apparatus having a quiescent condition and having an operating condition in which said mechanism responds to an applied key signal to effect decoding of the coded signal, and a key-signal source for supplying to said mechanism during intervals of reception of the coded television signal a key signal related to the coding schedule of the coded signal; an enunciator, a control circuit for actuating said enunciator, means for energizing said control circuit during any portion of the aforesaid reception intervals in which said decoding mechanism is in its quiescent condition; and means for disabling said control circuit when said decoding mechanism is in its operating condition.

2. In a receiver for utilizing a television signal coded in accordance with a prescribed coding schedule, an image-reproducing device, apparatus for receiving said television signal and for supplying said signal to said reproducing device, a, decoding mechanism coupled to said apparatus responsive to an applied key signal to efiect decoding of the coded signal, a key-signal source for producing during intervals of reception of the coded television signal a key signal related to the coding schedule of the coded signal, a switching device interposed between said source and said decoding mechanism operable from an open condition to a closed condition wherein said key signal from said source is supplied to said decoding mechanism, an enunciator, a control circuit for actuating said enunciator, means coupled to said switching device for energizing said control circuit during any portion of the aforesaid reception intervals in which said switching device is in its open condition; and means operable responsive to a closed condition of said switching device for disabling said control circuit when said decoding mechanism is in its operating condition.

8. In a receiver for utilizing a television signal coded in accordance with a prescribed coding schedule, an image-reproducing device, apparatus for receiving said television signal and for supplying said signal to said reproducing device, a decoding mechanism coupled to said apparatus having a quiescent condition and having an operating condition in which said mechanism responds to an applied key signal to effect decoding of the coded signal, a key-signal source for supplying to said mechanism during intervals of reception of the coded television signal a key signal related to the coding schedule of the coded signal, an enunciator, a control circuit for actuating said enunciator, means for coupling said control circuit to said key-signal source for energization thereby during any portion of the aforesaid reception intervals in which said decoding mechanism is in its quiescent condition; and means for disabling said control circuit when said decoding mechanism is in its operating condition.

JOHN R. HOWLAND.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,007,399 Koch July 9, 1935 2,297,205 Deserno Sept. 29, 1942 2,330,241 Roberts Sept. 28, 1943 2,364,357 Halstead Dec. 5, 1944 2,510,046 Ellett et a1 May 30, 1950 2,521,010 Homrighous Sept. 5, 1950 

